Color filters for use in liquid crystal display devices are provided with a light-shielding color filter called a black matrix, for the purpose of shielding transmission of light between colored pixels, improving contrast, or the like. In addition, solid-state imaging devices are also provided with a light-shielding film for the purpose of preventing generation of noise, improving image quality, or the like.
A black curable composition containing a black color material such as carbon black or titanium black is known as a composition for forming a black matrix for liquid crystal display devices, or a light-shielding color filter for solid-state imaging devices (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 10-246955, JP-A No. 9-54431, JP-A No. 10-46042, JP-A No. 2006-36750 and JP-A No. 2007-115921).
A black matrix for a liquid crystal display device is required to have light shieldability in, mainly, a visible-light region, whereas a light-shielding color filter for solid-state imaging devices is required to have light shieldability in an infrared region as well as in the visible-light region.
Furthermore, a next-generation light-shielding color filter for solid-state imaging devices is desired to have both improved light shieldability and reduced thickness. In order to satisfy both demands, it is necessary to increase the content of a black coloring material in a black curable composition.
However, if the content of a black coloring material in a conventional black curable composition for forming a light-shielding color filter for a solid-state imaging device is increased, light necessary for decomposition of a polymerization initiator is shielded and the content of curing components are relatively decreased, resulting in insufficient curing of, in particular, the periphery of a pattern (i.e., the boundary between the unexposed portion and the exposed portion). For these reasons, it was found that, although the pattern may be formed, a portion of a pattern is defective. In order to improve pattern defects, if the exposure light dose is increased to improve curing property, it was found that curing proceeds even in an unexposed portion and correspondingly a pattern size is increased, and consequently a desired pattern size cannot be formed, and residues are generated in the unexposed portion.
JP-A No. 2010-6932 and JP-A No. 2004-37986 disclose a photosensitive composition containing a resin with a specific structure having an acid group and an amino group for the purpose of improving dispersibility, reducing residues in the unexposed portion and the like. Further, an improvement in the pattern formability is required for a curable composition used for the formation of a light-shielding region in a solid-state imaging device.
In recent years, a small and thin imaging unit has been mounted on a portable terminal of electronic equipment such as a mobile phone or PDA (Personal Digital Assistant). Such an imaging unit is typically equipped with a solid-state imaging device such as a Charge Coupled Device (CCD) image sensor or Complementary Metal-Oxide Semiconductor (CMOS) image sensor, and a lens for making an image of the subject on the solid-state imaging device.
With the miniaturization and thickness reduction of portable terminals and propagation of portable terminals, further miniaturization and thickness reduction are also required for imaging units mounted thereon, and productivity is required. To cope with such demands, there is known a method for mass production of an imaging unit in which a lens substrate having plural lenses formed thereon and a sensor substrate having plural solid-state imaging devices formed thereon are integrally combined, and then the lens substrate and the sensor substrate are cut in such a manner that each of the cut substrates includes a lens and a solid-state imaging device. Further, as another method of producing an imaging unit, there is known a method in which only the lenses are produced on a glass wafer or the like, cut into an appropriate size for combination with individual sensors, and then combined with imaging devices which have been individualized in advance, a method in which plural lenses are formed in a mold using only a resin, and the lenses are combined on a sensor substrate, followed by cutting, a method in which lenses are cut into a size for combination with individual sensors, and then combined with imaging devices which have been individualized in advance, or the like.
Conventionally, as a wafer level lens array made up of a lens substrate and a lens group (a group of lenses) formed on the lens substrate, there is known one in which a curable resin material is added dropwise on a surface of a parallel plate substrate formed of a light-transmissive material such as glass, the resin material is formed into a given shape in a mold and then cured to form plural lenses (for example, see Japanese Patent No. 3926380 and International Publication No. WO 2008/102648). A region other than a lens section of the wafer level lens, or a portion of the lens may be provided with a light-shielding region formed of a black film, a metal film, or the like, in order to control an amount of light. Further, a fine pattern having a size of 50 μm or less may be formed on the same substrate, depending on applications for use. The light-shielding region is generally formed by coating a curable light-shielding composition using a photolithographic method or depositing a metal.
As a method of forming a light-shielding region using a photolithographic method, there is known a method of forming a light-shielding region constituted by a light-shielding film in which a light-shielding composition is coated onto a lens or a substrate such as a glass substrate, the portion that serves as a light-shielding region is subjected to exposure and curing, and then the light-shielding composition of the unexposed portion is removed using an alkaline developer. However, the formation of a light-shielding film using a conventional curable composition has a problem associated with low adhesion of a fine pattern on the same substrate. On the other hand, when a light-shielding film is formed in a high-exposure dose region necessary for the formation of a fine pattern, there is a problem in that curing proceeds also in a developed portion which is an unexposed portion, and residues remain. In other words, it is difficult to form both a light-shielding film (large pattern) and a fine pattern on the same substrate.
JP-A No. 2010-6932 and JP-A No. 2004-37986 disclose a photosensitive composition containing a resin with a specific structure having an acid group and an amino group for the purpose of improving dispersibility, reducing residues in the unexposed portion and the like. Further, an improvement in the pattern formability is required for a curable composition used for the formation of a light-shielding region in a wafer level lens having a large pattern and a fine pattern on the same substrate.